1. Field of the Invention
This invention relates generally to the field of packaging and containers, and, more specifically, to the manufacturing of cans using the double seaming process.
2. Description of the Related Technology
Conventionally, cans are sealed by applying a lid using the well-known double seaming process. This is most typically performed on a rotational type machine having multiple spindles. Each spindle or station contains a seaming chuck which acts as an anvil to support the can end unit while two freely rotating round seaming rolls are brought into contact towards the can axis using a cam motion. Each of the seaming rolls is formed with specific groove geometry to work the metal into what is a commercially accepted double seam. The seaming rolls are mounted in bearings and are rotated co-incident to contact with the can body and the end unit. This diameter is reduced in the act of double seaming and leaves a smooth, well rounded edge to the juncture of the can body and end unit. Latest metals technology has allowed for plastic laminates and specialized coatings to be applied to the steel. This protects the steel from oxidation in wet, damp environments. However, these laminates and coatings are upset in the double seaming process. Due to the nature of metal formation, heat is produced in each of the two seaming operations. This resultant heat produced in the first operation of seaming softens the laminate or coating and sets it up for damage in the second operation. The mode of failure is caused by the transfer of inertia to the second operation seaming roll while the coating or laminate is thermally elevated. Performing the second operation double seam generates even more thermal load allowing even more damage to the coating or laminate after contact.
A need exists for an improved system and method for seaming containers that is less destructive to the coating or laminate on the metal than are the systems and methods conventionally in use.